When production from a well driven by a pump slows, it is necessary to determine whether the production tubing is leaking, or whether the pump, such as a progressive cavity pump, is failing.
Typically, the tubing is tested by pulling the rods from the tubing and using an inspection truck to check the integrity of all the tubing joints. This process is slow as they can only pull so fast to get good readings, and weak joints have been missed even with this method. This process is relatively time consuming and expensive. Prior to this approach, the production tubing would be checked by pulling all the tubing and production pump from the well, then putting a plug and tubing drain on the bottom. The tubing would be run in ten joints at a time and pressure tested with water. If it did not fill, it would be pulled back up until the leak was located. The tubing would be run it ten joints at a time, and the few bad joints would be replaced. The drain plug was generally blown to speed up the re-pulling of the tubing string.